Add a zk-shell debug script

This is like the real zk-shell except:

1) It supports SSL
2) It automatically decompresses znodes if necessary
3) It handles sharded data
4) It doesn't have many commands

Change-Id: I2124f216f08f68ca63b763cd6f6adce452c07f79

tools/zk-shell.py

@@ -0,0 +1,179 @@
+# Copyright 2022 Acme Gating, LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+# Inspect ZK contents like zk-shell; handles compressed and sharded
+# data.
+
+import argparse
+import pathlib
+import cmd
+import sys
+import textwrap
+import zlib
+
+import kazoo.client
+from kazoo.exceptions import NoNodeError
+
+
+def resolve_path(path, rest):
+    newpath = path / rest
+    newparts = []
+    for part in newpath.parts:
+        if part == '.':
+            continue
+        elif part == '..':
+            newparts.pop()
+        else:
+            newparts.append(part)
+    return pathlib.PurePosixPath(*newparts)
+
+
+class REPL(cmd.Cmd):
+    def __init__(self, args):
+        self.path = pathlib.PurePosixPath('/')
+        super().__init__()
+        kwargs = {}
+        if args.cert:
+            kwargs['use_ssl'] = True
+            kwargs['keyfile'] = args.key
+            kwargs['certfile'] = args.cert
+            kwargs['ca'] = args.ca
+        self.client = kazoo.client.KazooClient(args.host, **kwargs)
+        self.client.start()
+
+    @property
+    def prompt(self):
+        return f'{self.path}> '
+
+    def do_EOF(self, path):
+        sys.exit(0)
+
+    def do_ls(self, path):
+        'List znodes: ls [PATH]'
+        if path:
+            mypath = self.path / path
+        else:
+            mypath = self.path
+        try:
+            for child in self.client.get_children(str(mypath)):
+                print(child)
+        except NoNodeError:
+            print(f'No such node: {mypath}')
+
+    def do_cd(self, path):
+        'Change the working path: cd PATH'
+        if path:
+            newpath = resolve_path(self.path, path)
+            if self.client.exists(str(newpath)):
+                self.path = newpath
+            else:
+                print(f'No such node: {newpath}')
+
+    def do_pwd(self):
+        'Print the working path'
+        print(self.path)
+
+    def help_get(self):
+        print(textwrap.dedent(self.do_get.__doc__))
+
+    def do_get(self, args):
+        """\
+        Get znode value: get PATH [-v]
+
+        -v: output metadata about the path
+        """
+        args = args.split(' ')
+        path = args[0]
+        args = args[1:]
+        path = resolve_path(self.path, path)
+        try:
+            compressed_data, zstat = self.client.get(str(path))
+        except NoNodeError:
+            print(f'No such node: {path}')
+            return
+        was_compressed = False
+        try:
+            data = zlib.decompress(compressed_data)
+            was_compressed = True
+        except zlib.error:
+            data = compressed_data
+        if '-v' in args:
+            print(f'Compressed: {was_compressed}')
+            print(f'Size: {len(data)}')
+            print(f'Compressed size: {len(compressed_data)}')
+            print(f'Zstat: {zstat}')
+        print(data)
+
+    def help_unshard(self):
+        print(textwrap.dedent(self.do_unshard.__doc__))
+
+    def do_unshard(self, args):
+        """\
+        Get the unsharded value: get PATH [-v]
+
+        -v: output metadata about the path
+        """
+        args = args.split(' ')
+        path = args[0]
+        args = args[1:]
+        path = resolve_path(self.path, path)
+
+        try:
+            shards = sorted(self.client.get_children(str(path)))
+        except NoNodeError:
+            print(f'No such node: {path}')
+            return
+        compressed_data = b''
+        data = b''
+        for shard in shards:
+            d, _ = self.client.get(str(path / shard))
+            compressed_data += d
+        if compressed_data:
+            data = zlib.decompress(compressed_data)
+
+        if '-v' in args:
+            print(f'Size: {len(data)}')
+            print(f'Compressed size: {len(compressed_data)}')
+        print(data)
+
+    def do_rm(self, args):
+        'Delete znode: rm PATH [-r]'
+        args = args.split(' ')
+        path = args[0]
+        args = args[1:]
+        path = resolve_path(self.path, path)
+        if '-r' in args:
+            recursive = True
+        else:
+            recursive = False
+        try:
+            self.client.delete(str(path), recursive=recursive)
+        except NoNodeError:
+            print(f'No such node: {path}')
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('host', help='ZK host string')
+    parser.add_argument('--cert', help='Path to TLS certificate')
+    parser.add_argument('--key', help='Path to TLS key')
+    parser.add_argument('--ca', help='Path to TLS CA cert')
+    args = parser.parse_args()
+
+    repl = REPL(args)
+    repl.cmdloop()
+
+
+if __name__ == '__main__':
+    main()